Preparation of free-suspended polyelectrolyte multilayer films using an alginate scaffold and their ion permeability

Free-suspended polyelectrolyte multilayer (PEM) films were prepared over an aperture (diameter, 1 or 3 mm) in a glass plate to study ion permeation across the PEM films. PEM films were successfully constructed by layer-by-layer deposition of poly(allylamine hydrochloride) and poly(styrene sulfonate) on the surface of glass plate whose aperture had been filled with an alginate gel, followed by dissolution of the alginate gel in an ethylenediaminetetraacetic acid solution. PEM films thus prepared showed selective permeability for inorganic salts such as NaCl, KCl, CaCl2, Na2SO4, K3[Fe(CN)6], and K4[Fe(CN)6]. The results were rationalized based on the size and charge of the ions and the thickness and surface charges of films.